Method for generating scanning path of machining feature surface of aircraft panel

Abstract

A method for generating a scanning path of a machining feature surface of an aircraft panel, including: acquiring a main direction and a triangular mesh model of the aircraft panel; dividing the triangular mesh model into multiple regions; recognizing the machining feature surface according to the main direction; projecting the machining feature surface to a 2D coordinate system thereof; extracting a 2D scanning path for the machining feature surface; and mapping the 2D scanning path to a 3D space to generate a 3D scanning path.

What is claimed is: 
     
       1. A method for generating a scanning path of a machining feature surface of an aircraft panel, comprising:
 (S 1 ) horizontally placing an aircraft panel to be scanned on a scanning platform; and acquiring a triangular mesh model of the aircraft panel to be scanned; 
 wherein an upward direction perpendicular to the scanning platform is taken as a main direction of the aircraft panel; and 
 the triangular mesh model is composed of a plurality of triangular facets; 
 (S 2 ) dividing the triangular mesh model into a plurality of regions; 
 (S 3 ) taking a mean value of normal vectors of the plurality of triangular facets in each of the plurality of regions as a normal vector of a corresponding region, wherein a region with a normal vector perpendicular to the main direction of the aircraft panel is taken as a machining feature surface; 
 (S 4 ) projecting the machining feature surface to a two-dimensional (2D) local coordinate system thereof; and extracting a 2D scanning path for the machining feature surface; and 
 (S 5 ) mapping the 2D scanning path to a 3D space to generate the 3D scanning path of the machining feature surface. 
 
     
     
       2. The method of  claim 1 , wherein the step (S 2 ) is performed through steps of:
 (S 2 . 1 ) for an edge of each of the plurality of triangular facets in the triangular mesh model, calculating a normal vector of two triangular facets sharing the edge, respectively; 
 (S 2 . 2 ) calculating an angle between normal vectors of the two triangular facets, wherein if the angle is greater than a preset threshold, the two triangular facets are marked as different regions; if the angle is equal to or less than the preset threshold, whether the two triangular facets have been marked is determined, and if at least one of the two triangular facets has not been marked, the two triangular facets are marked as the same region, and if the two triangular facets both have been marked but not in the same region, two regions respectively corresponding to the two triangular facets are marked as the same region; and 
 (S 2 . 3 ) traversing edges of the plurality of triangular facets to complete region division of the triangular mesh model. 
 
     
     
       3. The method of  claim 2 , wherein a normal vector n of each of the plurality of triangular facets is calculated as follows: 
       
         
           
             
               
                 n 
                 = 
                 
                   
                     ( 
                     
                       
                         v 
                         ⁢ 
                         2 
                       
                       - 
                       
                         v 
                         ⁢ 
                         1 
                       
                     
                     ) 
                   
                   * 
                   
                     ( 
                     
                       
                         v 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         3 
                       
                       - 
                       
                         v 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         1 
                       
                     
                     ) 
                   
                 
               
               ; 
             
           
         
         wherein v 1 , v 2  and v 3  are three nodes of each of the plurality of triangular facets. 
       
     
     
       4. The method of  claim 1 , wherein in step (S 4 ), the 2D local coordinate system of the machining feature surface is built through the following steps:
 obtaining eigenvalues and eigenvectors of a covariance matrix corresponding to a data matrix formed by coordinates of nodes of all triangular facets on the machining feature surface by principal component analysis; taking an eigenvector corresponding to a largest eigenvalue as an x-axis of the 2D local coordinate system; taking an eigenvector corresponding to a second-largest eigenvalue as a y-axis of the 2D local coordinate system; and taking a mean center of the machining feature surface as an origin point of the 2D local coordinate system. 
 
     
     
       5. The method of  claim 1 , wherein in step (S 4 ), the 2D scanning path is extracted through steps of:
 (S 4 . 1 ) performing an equal-interval sampling on an x-axis covered by the machining feature surface in the 2D local coordinate system; 
 (S 4 . 2 ) drawing a straight line parallel to a y-axis of the 2D local coordinate system and passing through the machining feature surface on each sampling point; and taking the straight line as a projection line; 
 (S 4 . 3 ) forming intersections between the projection line and an edge of the plurality of triangular facets of the machining feature surface; and taking a mean coordinate of two intersections at a boundary of the machining feature surface as a scanning point corresponding to a sampling point; 
 (S 4 . 4 ) pointing a direction vector of the scanning point to a next scanning point in sequence until a final direction vector points to a last scanning point to acquire the 2D scanning path for the machining feature surface; and 
 (S 4 . 5 ) repeating steps (S 4 . 1 )-(S 4 . 4 ) to obtain 2D scanning paths for all machining feature surfaces of the aircraft panel. 
 
     
     
       6. The method of  claim 5 , wherein the equal-interval sampling is performed at an interval of 2 cm.